system specs to play il-2 smoothly at 2560*1600?

[Flyby]

don't know if this helps, but I think you have more of a problem with graphics memory than with processor ghz. but yeah, IL2 will only use one core so the more ghz the better. follow this link to Hard_OCP. there is a list of graphics cards for you to review. the new ATi cards are there, but may I suggest you look at the ATi 4890 too? Of course it depends on your wallet. any card you check out here will also show the competition's results to. Most cards there seem to be tested (also) at 25x12 resolution so you should be able to compare easily. use the drop-down menu to view results for specific games. here ya go: http://www.hardocp.com/reviews/gpu_video_cards/
now be sure to tell us all what you decide to go with.
Flyby out
ps be sure to look at the test system being used for these graphics cards. it may provide a nice idea for a system upgrade too.